1. Field of the Invention
The present invention relates to surface-treated sodium bicarbonate particles, and, more particularly, to surface-treated sodium bicarbonate particles exhibiting an increased capacity to bind with other sodium bicarbonate particles as well as with other components when they are molded. The invention also relates to molded preparations comprising such surface-treated sodium bicarbonate particles.
2. Description of the Background
Sodium bicarbonate is very frequently molded into tablets, granules, or the like for use as effervescent tablets of bathing agents, digesting agents, gargles, vaginal agents, etc. Sodium bicarbonate particles, however, possess only a poor capacity to bind with other sodium bicarbonate particles or with other components, resulting in difficulties in molding operations, especially in high-speed molding operations. For this reason, the use of a considerable amount of binder has been imperative for molding compositions containing sodium bicarbonate particles. The use of a large amount of binder, however, inevitably results in a decrease in the sodium bicarbonate amount in a molded product. This necessitates the administration of a large amount of a drug to the user, thus producing them a disagreeable feeling. Production costs also increase as a result of the use of such a large amount of binder.
Although various studies directed t the development of binders exhibiting a higher binding effect have been undertaken, none of these studies have so far been successful.
In view of this situation, the present inventors have undertaken extensive studies, and, as a result, have found that the binding capacity of sodium bicarbonate particles could remarkably be improved by coating their surfaces with sodium carbonate or its double salt. Such a finding has led to the completion of the present invention.